1. Field of the Invention
The present invention relates to a substrate on which a BGA (Ball Grid Array) type electrical part is mounted, and a method for mounting the BGA type electrical part on the substrate.
2. Description of the Related Art
A plurality of electrodes is mounted on a rear surface of a BGA electrical part. A plurality of lands is mounted on a front surface of a substrate on which the BGA electrical part is mounted. An array of the electrodes and an array of the lands are matched with each other. The electrode is connected to the land through solder. This connection enables the BGA electrical part to be fixed to the substrate.
The technique for mounting the BGA electrical part on the substrate is disclosed in Japanese Laid Open Patent Applications JP-A-H7-147481, JP-A-H8-125325, JP-A-H9-45805, JP-A-H10-163371 and JP-AH11-74637 and Japanese Patent Application Filing Number H10-346025 corresponding to U.S. patent application Filing Ser. No. 09/435,448. Those documents disclose the technique for connecting one land to one electrode.
The mounting of the BGA electrical part on the substrate requires a countermeasure for protecting a crack caused by heat cycle stress. The mounting of the BGA electrical part requires a countermeasure for protecting a damage caused by external stress. Those countermeasures are done by using a curing agent or a resin adhesive (hereafter, merely referred to as an adhesive). If the adhesive is filled between the BGA electrical part and the substrate, it is possible to improve the bond strength between the BGA electrical part and the substrate.
Increase in a mount density of the substrate causes an interval between the BGA electrical part and a peripheral part to be narrow. If the interval is narrow, the adhesive for the BGA electrical part comes in contact with the peripheral part. The adhesive disturbs the radiation from the peripheral part. The adhesive semi-permanently attaches the BGA electrical part and the peripheral part to the substrate. The BGA electrical part and the peripheral part are not easily dismounted from the substrate. If trouble is induced in the BGA electrical part and the peripheral part, it is impossible to replace the BGA electrical part and the peripheral part.
The applicant already filed a patent with regard to an invention for improving bond strength without using an adhesive (Japanese Patent Application Filing Number H10-346025). This application discloses a substrate (printed circuit substrate) is provided with a normal land to which a normal electrode of a BGA electrical part is bonded and an integrated land to which a plurality of integrated electrodes of the electrical part are bonded. Bond strength between the BGA electrical part and the electrode is stronger than bond strength between the substrate and the land. Bond strength between the substrate and the BGA electrical part depends on the bond strength between the substrate and the land. Its bond strength has a value that has no influence on a usual usage environment. The occurrences of a strong force for stripping the BGA electrical part from the substrate causes the BGA electrical part together with the land to be stripped from the substrate.
It is an object of the present invention is to provide a substrate on which the BGA type electrical part is mounted and a method for mounting the electrical part on the substrate. On the substrate and in the method, the BGA electrical part together with the land is never stripped by the heat cycle stress from the substrate.
In order to achieve an aspect of the present invention, a substrate on which a ball grid allay type electrical part is mounted includes a substrate body (2), a normal land (3), an integrated land (4) and connection reinforcement section (5). The substrate body (2) provided with a ball grid allay type electrical part. On the normal land (3), a normal electrode (12) of the ball grid array type electrical part (10) is connected. On the integrated land (4), a plurality of integrated electrodes (13) of the ball grid allay type electrical part (10) is connected. The connection reinforcement section (5) connects to the integrated land (4) to the substrate body (2).
In the above substrate, the connection reinforcement section (5) is a through section which pierces the integrated land and the substrate body.
In the above substrate, the connection reinforcement section (5) is a convexity section which pass through the integrated land to inside of the substrate body.
In the above substrate, the integrated land (4) has a surface area which is wider than a surface area of the normal land (3).
In the above substrate, the integrated land (4) is a grounding land supplying a ground potential.
In the above substrate, the integrated land (4) is a power supply land supplying a power potential.
In the above substrate, the integrated land (4) is a signal land supplying a data signal.
In the above substrate, the connection reinforcement section (5) is a through pipe which pierces the integrated land and the substrate body from a front surface of the substrate body to a rear surface thereof.
In the above substrate, the connection reinforcement section is a retiring shape section which pierces the integrated land and is embedded in the substrate body.
In order to achieve an aspect of the present invention, a method of mounting ball grid array type electrical part on substrate includes connecting of a normal electrode (12) of a ball grid allay type electrical part to normal land. The method further includes connecting a plurality of connecting integrated terminals (13) of a ball grid allay type electrical part to an integrated land of a substrate body (2). In the connecting of the normal electrode (12), the normal electrode (12) of a ball grid array type electrical part (10) is connected on a normal land (3) of a substrate body (2) via a connecting material (22). In the connecting of the plurality of integrated terminals (13), the plurality of integrated terminals (13) of the ball grid array type electrical part (10) is connected on an integrated land (4). The integrated land (4) is connected to a substrate body (2) by a connection reinforcement section (5).
In the above method, the connecting material (22) is made of a solder.
In the above method, the connection reinforcement section (5) has a through pipe which pierces the integrated land (4) and the substrate body (2). The connecting material (22) is flowed into the through pipe.
In the above method, the connection reinforcement section (5) has a retiring shape section which pierces the integrated land (4) and retires the substrate body (2). The connecting material (22) is flowed into the connection reinforcement section (5).
In the above method, a surface area of the integrated land (4) is wider than a surface area of the normal land (3).
In the above method, a ground potential for the ball grid array type electrical part (10) is applied to the integrated land (4).
In the above method, a power potential for the ball grid array type electrical part (10) is applied to the integrated land (4).
In the above method, a data signal for the ball grid array type electrical part (10) is supplied to the integrated land (4).
In the above method, the connection reinforcement section (5) is a through pipe which pierces the integrated land (4) and the substrate body (2) from a front surface of the substrate body (2) to a rear surface thereof.
In the above method, the connection reinforcement section (5) is a retiring shape section which pierces the integrated land and is embedded in the substrate body (2)